Heretofore, a multimode ultrasonic actuator has been known (see Patent Document 1) that oscillates separately in a driving direction and a pressing direction. The principle of driving of this multimode ultrasonic actuator combines oscillations in a direction parallel to the driving direction of a moving element (torsional oscillations) and oscillations in a direction parallel to a pressing direction (longitudinal oscillations).
The multimode ultrasonic actuator pushes up the moving element with displacements caused by vertical oscillations generated in an oscillating element, at the same time generates displacements of the moving element by torsional oscillations of the oscillating element in the same direction as the driving direction of the moving element, and thus drives the moving element. The vertical oscillations also oscillate in the opposite direction to the direction of pushing up the moving element. Consequently, the oscillating element and the moving element separate when the oscillating element oscillates in the opposite direction. In this period, the oscillating element is displaced by the torsional oscillation in a direction opposite to the driving direction of the moving element. Thus, by the vertical oscillations and the torsional oscillations being combined, the moving element is driven one way in a desired direction.
A piezoelectric actuator has also been disclosed (see Patent Document 2) that combines two piezoelectric elements to drive a moving element. In Patent Document 2, a piezoelectric actuator combines a piezoelectric slip effect element with a piezoelectric lateral effect element. In this piezoelectric actuator, the piezoelectric slip effect element is displaced in the driving direction of a moving element, the piezoelectric lateral effect element is displaced in a pressing direction, and the moving element is driven by the combination thereof.    [Patent Document 1] Japanese Unexamined Patent Application, Publication No. H09-84367    [Patent Document 2] Japanese Unexamined Patent Application, Publication. No. S62-71480